The present invention relates to process control transmitters operating in the process control industry. In particular, the invention relates to transmitter built-in test equipment useful in solving malfunctions or failures of microprocessor-based process control transmitters.
Efficient manipulation of a process variable in a controlled process requires that faults in a transmitter or its related transducer or communication circuits be identified immediately so that appropriate corrective action or appropriate warnings may be implemented. Verification of a malfunction or error prior to stopping the process and removing a transmitter from a process loop provides inherent efficiency. Present microprocessor-based transmitters contain complex electrical circuits that sometimes appear to have failed, while actually only a leakage or shunted electrical current has occurred. For example, a circuit leakage current that affects loop current may be reported as a transmitter fault.